Endless belt conveyors which are used to convey bulk materials on the belt generally discharge the material as the belt moves over the head pulley of the conveyor.
The endless belt, except in very small sizes, comprises a length of belting having its ends spliced or seamed. The belting used in a belt filter is of a porous weave which cannot practicably be spliced and requires a well designed seam because of the relatively fragile nature of the belting and the considerable belt tension which is required for the operation of the filter press. A hinged joint is required because of the small radius of the many rolls over which the belt travels in a belt filter.
The typical hinged belt joint includes two series of clips and a connecting hinge pin or hinge wire. The clips and the pin extend the width of the belt and each clip essentially comprises a staple which grasps the adjacent end portions of the belting. The staples may be clinched for additional security. The clips must securely grasp the adjacent ends of the belting which are of a multiple thickness for added strength. For reference purposes, one clip extends forwardly having reference to the direction of belt travel. In another type of seam, a series of loops is sewn in each of the two adjoining ends of the belting so that a stiff wire or plastic pin may be passed through the loops to form the joint.
The materials to be belt filtered particularly tend to stick to the belt and require their removal with a doctor blade which is held against or immediately adjacent to the carrying surface of the belt so that the material is fully removed with a minimum of residue.
Preferably such a doctor blade comprises a flat, rigid bar having a bevelled edge. The doctor blade is pivotally mounted and spring biased so that its bevelled edge is held in contact with the belt where it is firmly supported by a roll. The blade is preferably of a non-metallic material so that its contact with the belt will not damage the belt.
A considerable difficulty in the operation of the filter belt has been due to the damaging effect of the belt seam on the doctor blade as it approaches and lifts and then passes under the blade. Additionally, if some part of either clip is projecting it often catches on the doctor blade such that both the blade and the belt are damaged and require repair.
The object of the present invention is to prevent such damage to the doctor blade and to the belt and clips by providing reliable means for lifting the doctor blade at least over the forward portion of the seam. In particular such means should operate irrespective of whether the belt seam has remained normal or straight across the belt or has become skewed, as is usual to some degree.